Most of antennas used in conventional wireless LAN (Local Area Network) systems and Ultra-wideband (UWB) wireless systems depend on characteristics of frequency bands used in the systems and have directivity of relatively wide angles. Therefore, applications that can be used in and environments that can be applied to the systems are varied and expected to continue to spread in future. However, there is an increasing demand for an increase in transmission speed of wireless communication in recent years. Wireless communication systems that use a millimeter wave band and the like in which an ultra-wideband can be secured are examined (e.g., IEEE 802.15.3c).
Compared with a microwave band, the millimeter wave band has advantages that directivity is high and the influence of interference is small, and security can be assured. In the past, as an alternative of wired communication, the millimeter wave band is used in a part of inter-building communication (see FIG. 59), a video transmission system for home televisions, and the like. As standards, “ARIB STD-T69”, “ARIB STD-T74”, and the like are specified.
In general, attenuation of power in a space is larger in the millimeter wave band compared with the microwave band and the like. Therefore, communication areas are limited and environments of use and applications are limited. Because of a relatively narrow directional pattern (also referred to as directional beam or antenna beam), a carrier or the like needs to set a wireless apparatus with directivity thereof adjusted in advance.
On the other hand, after the wireless apparatus is set, it is likely that adjustment of directivity is necessary because of a change in environment or the like. Therefore, a technology for realizing efficient adjustment of directivity is also examined (e.g., Patent Documents 1 and 2). Patent Document 1 discloses a technology for, in parallel to path control, realizing efficiency by adjusting directivity using a general antenna control technology. Patent Document 2 discloses a technology for setting directional beams opposite to each other between terminal stations by controlling directional antennas based on location information or the like received from communication partners.
In the past, to realize improvement of physical transmission speed, a multi-value modulation system, spatial multiplexing (MIMO), wider band, and the like have been adopted. To realize MAC efficiency matching the transmission speed, configuration of Superframe, improvement an access system, improvement of an ARQ system, and the like have been performed for each of systems.
Among the measures, as a MAC technology for improving transmission efficiency according to transmission speed, a frame aggregation technology for coupling a plurality of short packets as one large packet and transmitting the packet is proposed. In the conventional wireless LAN system, an A-MSDU (Aggregate MAC Service Data Unit) system and an A-MPDU (Aggregate MAC Protocol Data Unit) system are proposed in a standard called IEEE 802.11n (e.g., Nonpatent Document 1). A frame aggregation technology for MSDU is also proposed in an ultra-wideband wireless system (see Nonpatent Document 2).    Patent Document 1: Japanese Patent Application Laid-open No. 2003-309508    Patent Document 2: Japanese Patent Application Laid-open No. 2004-32062    Nonpatent Document 1: IEEE 802.11n-Draft1.06, Section 7.2.2.1, A-MSDU, Section 7.4 A-MPDU    Nonpatent Document 2: High Rate Ultra-wideband PHY and MAC Standard, (ECMA-368, 369)